1. Field of the Invention
The present invention relates generally to digital filters, and more particularly, to decimation filters.
2. Related Art
A multirate system processes signals at different sample rates, and typically includes one or more sample rate converters for converting between the different sample rates. A sample rate converter often includes a decimation filter. The decimation filter (also referred to as a decimator) receives an input signal having an input sample rate, frequency band-limits the input signal, and downsamples the input signal by a predetermined downsampling factor (also referred to as a decimation factor). Thus, the decimator produces a band-limited output signal having an output sample rate equal to the input sample rate divided by the downsampling factor. The process performed by the decimator is referred to as “decimation filtering,” or just “decimation.”
A popular type of decimation filter is a Cascaded Integrator-Comb (CIC) filter. The CIC filter is popular because it achieves generally acceptable decimation results while using a relatively simple structure as compared to some other types of conventional decimation filters. The CIC filter can be implemented using digital circuits. Generally, it is desirable that digital circuits consume as little power as possible. This is especially true where such digital circuits are associated with a multirate system constructed on an integrated circuit (IC). Therefore, there is a need for an improved decimation filter that consumes less power than a CIC filter, while achieving a decimation result that is the same as, or at least substantially the same as, that of the CIC filter.